[PATCH] audit signal recipients

When auditing syscalls that send signals, log the pid and security
context for each target process. Optimize the data collection by
adding a counter for signal-related rules, and avoiding allocating an
aux struct unless we have more than one target process. For process
groups, collect pid/context data in blocks of 16. Move the
audit_signal_info() hook up in check_kill_permission() so we audit
attempts where permission is denied.

Signed-off-by: Amy Griffis <amy.griffis@hp.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

4 files changed, 153 insertions, 29 deletions

diff --git a/kernel/audit.h b/kernel/audit.h
index a337023..815d6f5 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -83,6 +83,7 @@ struct audit_krule {
 	u32			field_count;
 	char			*filterkey; /* ties events to rules */
 	struct audit_field	*fields;
+	struct audit_field	*arch_f; /* quick access to arch field */
 	struct audit_field	*inode_f; /* quick access to an inode field */
 	struct audit_watch	*watch;	/* associated watch */
 	struct list_head	rlist;	/* entry in audit_watch.rules list */
@@ -131,17 +132,19 @@ extern void audit_handle_ievent(struct inotify_watch *, u32, u32, u32,
 extern int selinux_audit_rule_update(void);
 
 #ifdef CONFIG_AUDITSYSCALL
-extern void __audit_signal_info(int sig, struct task_struct *t);
-static inline void audit_signal_info(int sig, struct task_struct *t)
+extern int __audit_signal_info(int sig, struct task_struct *t);
+static inline int audit_signal_info(int sig, struct task_struct *t)
 {
-	if (unlikely(audit_pid && t->tgid == audit_pid))
-		__audit_signal_info(sig, t);
+	if (unlikely((audit_pid && t->tgid == audit_pid) ||
+		     (audit_signals && !audit_dummy_context())))
+		return __audit_signal_info(sig, t);
+	return 0;
 }
 extern enum audit_state audit_filter_inodes(struct task_struct *,
 					    struct audit_context *);
 extern void audit_set_auditable(struct audit_context *);
 #else
-#define audit_signal_info(s,t)
+#define audit_signal_info(s,t) AUDIT_DISABLED
 #define audit_filter_inodes(t,c) AUDIT_DISABLED
 #define audit_set_auditable(c)
 #endif
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 3749193..6c61263 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -311,6 +311,43 @@ int audit_match_class(int class, unsigned syscall)
 	return classes[class][AUDIT_WORD(syscall)] & AUDIT_BIT(syscall);
 }
 
+static inline int audit_match_class_bits(int class, u32 *mask)
+{
+	int i;
+
+	if (classes[class]) {
+		for (i = 0; i < AUDIT_BITMASK_SIZE; i++)
+			if (mask[i] & classes[class][i])
+				return 0;
+	}
+	return 1;
+}
+
+static int audit_match_signal(struct audit_entry *entry)
+{
+	struct audit_field *arch = entry->rule.arch_f;
+
+	if (!arch) {
+		/* When arch is unspecified, we must check both masks on biarch
+		 * as syscall number alone is ambiguous. */
+		return (audit_match_class_bits(AUDIT_CLASS_SIGNAL,
+					       entry->rule.mask) &&
+			audit_match_class_bits(AUDIT_CLASS_SIGNAL_32,
+					       entry->rule.mask));
+	}
+
+	switch(audit_classify_arch(arch->val)) {
+	case 0: /* native */
+		return (audit_match_class_bits(AUDIT_CLASS_SIGNAL,
+					       entry->rule.mask));
+	case 1: /* 32bit on biarch */
+		return (audit_match_class_bits(AUDIT_CLASS_SIGNAL_32,
+					       entry->rule.mask));
+	default:
+		return 1;
+	}
+}
+
 /* Common user-space to kernel rule translation. */
 static inline struct audit_entry *audit_to_entry_common(struct audit_rule *rule)
 {
@@ -429,6 +466,7 @@ static struct audit_entry *audit_rule_to_entry(struct audit_rule *rule)
 				err = -EINVAL;
 				goto exit_free;
 			}
+			entry->rule.arch_f = f;
 			break;
 		case AUDIT_PERM:
 			if (f->val & ~15)
@@ -519,7 +557,6 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
 		case AUDIT_FSGID:
 		case AUDIT_LOGINUID:
 		case AUDIT_PERS:
-		case AUDIT_ARCH:
 		case AUDIT_MSGTYPE:
 		case AUDIT_PPID:
 		case AUDIT_DEVMAJOR:
@@ -531,6 +568,9 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
 		case AUDIT_ARG2:
 		case AUDIT_ARG3:
 			break;
+		case AUDIT_ARCH:
+			entry->rule.arch_f = f;
+			break;
 		case AUDIT_SUBJ_USER:
 		case AUDIT_SUBJ_ROLE:
 		case AUDIT_SUBJ_TYPE:
@@ -1221,6 +1261,9 @@ static inline int audit_add_rule(struct audit_entry *entry,
 #ifdef CONFIG_AUDITSYSCALL
 	if (!dont_count)
 		audit_n_rules++;
+
+	if (!audit_match_signal(entry))
+		audit_signals++;
 #endif
 	mutex_unlock(&audit_filter_mutex);
 
@@ -1294,6 +1337,9 @@ static inline int audit_del_rule(struct audit_entry *entry,
 #ifdef CONFIG_AUDITSYSCALL
 	if (!dont_count)
 		audit_n_rules--;
+
+	if (!audit_match_signal(entry))
+		audit_signals--;
 #endif
 	mutex_unlock(&audit_filter_mutex);
 
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 2243c55..6aff0df 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -89,6 +89,9 @@ extern int audit_enabled;
 /* number of audit rules */
 int audit_n_rules;
 
+/* determines whether we collect data for signals sent */
+int audit_signals;
+
 /* When fs/namei.c:getname() is called, we store the pointer in name and
  * we don't let putname() free it (instead we free all of the saved
  * pointers at syscall exit time).
@@ -114,6 +117,9 @@ struct audit_aux_data {
 
 #define AUDIT_AUX_IPCPERM	0
 
+/* Number of target pids per aux struct. */
+#define AUDIT_AUX_PIDS	16
+
 struct audit_aux_data_mq_open {
 	struct audit_aux_data	d;
 	int			oflag;
@@ -181,6 +187,13 @@ struct audit_aux_data_path {
 	struct vfsmount		*mnt;
 };
 
+struct audit_aux_data_pids {
+	struct audit_aux_data	d;
+	pid_t			target_pid[AUDIT_AUX_PIDS];
+	u32			target_sid[AUDIT_AUX_PIDS];
+	int			pid_count;
+};
+
 /* The per-task audit context. */
 struct audit_context {
 	int		    dummy;	/* must be the first element */
@@ -201,6 +214,7 @@ struct audit_context {
 	struct vfsmount *   pwdmnt;
 	struct audit_context *previous; /* For nested syscalls */
 	struct audit_aux_data *aux;
+	struct audit_aux_data *aux_pids;
 
 				/* Save things to print about task_struct */
 	pid_t		    pid, ppid;
@@ -657,6 +671,10 @@ static inline void audit_free_aux(struct audit_context *context)
 		context->aux = aux->next;
 		kfree(aux);
 	}
+	while ((aux = context->aux_pids)) {
+		context->aux_pids = aux->next;
+		kfree(aux);
+	}
 }
 
 static inline void audit_zero_context(struct audit_context *context,
@@ -798,6 +816,29 @@ static void audit_log_task_info(struct audit_buffer *ab, struct task_struct *tsk
 	audit_log_task_context(ab);
 }
 
+static int audit_log_pid_context(struct audit_context *context, pid_t pid,
+				 u32 sid)
+{
+	struct audit_buffer *ab;
+	char *s = NULL;
+	u32 len;
+	int rc = 0;
+
+	ab = audit_log_start(context, GFP_KERNEL, AUDIT_OBJ_PID);
+	if (!ab)
+		return 1;
+
+	if (selinux_sid_to_string(sid, &s, &len)) {
+		audit_log_format(ab, "opid=%d obj=(none)", pid);
+		rc = 1;
+	} else
+		audit_log_format(ab, "opid=%d  obj=%s", pid, s);
+	audit_log_end(ab);
+	kfree(s);
+
+	return rc;
+}
+
 static void audit_log_exit(struct audit_context *context, struct task_struct *tsk)
 {
 	int i, call_panic = 0;
@@ -976,23 +1017,21 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
 		audit_log_end(ab);
 	}
 
-	if (context->target_pid) {
-		ab =audit_log_start(context, GFP_KERNEL, AUDIT_OBJ_PID);
-		if (ab) {
-			char *s = NULL, *t;
-			u32 len;
-			if (selinux_sid_to_string(context->target_sid,
-						    &s, &len))
-				t = "(none)";
-			else
-				t = s;
-			audit_log_format(ab, "opid=%d obj=%s",
-					context->target_pid, t);
-			audit_log_end(ab);
-			kfree(s);
-		}
+	for (aux = context->aux_pids; aux; aux = aux->next) {
+		struct audit_aux_data_pids *axs = (void *)aux;
+		int i;
+
+		for (i = 0; i < axs->pid_count; i++)
+			if (audit_log_pid_context(context, axs->target_pid[i],
+						  axs->target_sid[i]))
+				call_panic = 1;
 	}
 
+	if (context->target_pid &&
+	    audit_log_pid_context(context, context->target_pid,
+				  context->target_sid))
+			call_panic = 1;
+
 	if (context->pwd && context->pwdmnt) {
 		ab = audit_log_start(context, GFP_KERNEL, AUDIT_CWD);
 		if (ab) {
@@ -1213,7 +1252,10 @@ void audit_syscall_exit(int valid, long return_code)
 	} else {
 		audit_free_names(context);
 		audit_free_aux(context);
+		context->aux = NULL;
+		context->aux_pids = NULL;
 		context->target_pid = 0;
+		context->target_sid = 0;
 		kfree(context->filterkey);
 		context->filterkey = NULL;
 		tsk->audit_context = context;
@@ -1947,15 +1989,17 @@ int audit_avc_path(struct dentry *dentry, struct vfsmount *mnt)
  * If the audit subsystem is being terminated, record the task (pid)
  * and uid that is doing that.
  */
-void __audit_signal_info(int sig, struct task_struct *t)
+int __audit_signal_info(int sig, struct task_struct *t)
 {
+	struct audit_aux_data_pids *axp;
+	struct task_struct *tsk = current;
+	struct audit_context *ctx = tsk->audit_context;
 	extern pid_t audit_sig_pid;
 	extern uid_t audit_sig_uid;
 	extern u32 audit_sig_sid;
 
-	if (sig == SIGTERM || sig == SIGHUP || sig == SIGUSR1) {
-		struct task_struct *tsk = current;
-		struct audit_context *ctx = tsk->audit_context;
+	if (audit_pid && t->tgid == audit_pid &&
+	    (sig == SIGTERM || sig == SIGHUP || sig == SIGUSR1)) {
 		audit_sig_pid = tsk->pid;
 		if (ctx)
 			audit_sig_uid = ctx->loginuid;
@@ -1963,4 +2007,33 @@ void __audit_signal_info(int sig, struct task_struct *t)
 			audit_sig_uid = tsk->uid;
 		selinux_get_task_sid(tsk, &audit_sig_sid);
 	}
+
+	if (!audit_signals) /* audit_context checked in wrapper */
+		return 0;
+
+	/* optimize the common case by putting first signal recipient directly
+	 * in audit_context */
+	if (!ctx->target_pid) {
+		ctx->target_pid = t->tgid;
+		selinux_get_task_sid(t, &ctx->target_sid);
+		return 0;
+	}
+
+	axp = (void *)ctx->aux_pids;
+	if (!axp || axp->pid_count == AUDIT_AUX_PIDS) {
+		axp = kzalloc(sizeof(*axp), GFP_ATOMIC);
+		if (!axp)
+			return -ENOMEM;
+
+		axp->d.type = AUDIT_OBJ_PID;
+		axp->d.next = ctx->aux_pids;
+		ctx->aux_pids = (void *)axp;
+	}
+	BUG_ON(axp->pid_count > AUDIT_AUX_PIDS);
+
+	axp->target_pid[axp->pid_count] = t->tgid;
+	selinux_get_task_sid(t, &axp->target_sid[axp->pid_count]);
+	axp->pid_count++;
+
+	return 0;
 }
diff --git a/kernel/signal.c b/kernel/signal.c
index 2ac3a66..c43a3f1 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -497,6 +497,11 @@ static int check_kill_permission(int sig, struct siginfo *info,
 	int error = -EINVAL;
 	if (!valid_signal(sig))
 		return error;
+
+	error = audit_signal_info(sig, t); /* Let audit system see the signal */
+	if (error)
+		return error;
+
 	error = -EPERM;
 	if ((info == SEND_SIG_NOINFO || (!is_si_special(info) && SI_FROMUSER(info)))
 	    && ((sig != SIGCONT) ||
@@ -506,10 +511,7 @@ static int check_kill_permission(int sig, struct siginfo *info,
 	    && !capable(CAP_KILL))
 		return error;
 
-	error = security_task_kill(t, info, sig, 0);
-	if (!error)
-		audit_signal_info(sig, t); /* Let audit system see the signal */
-	return error;
+	return security_task_kill(t, info, sig, 0);
 }
 
 /* forward decl */